What Is Hardware-In-The-Loop Simulation?

Hardware-in-the-loop (HIL) simulation is a type of real-time
simulation. You use HIL simulation to test your controller design.
HIL simulation shows how your controller responds, in real time, to
realistic virtual stimuli. You can also use HIL to determine if your
physical system (plant) model is valid.

In HIL simulation, you use a real-time computer as a virtual
representation of your plant model and a real version of your controller.
The figure shows a typical HIL simulation setup. The desktop computer
(development hardware) contains the real-time capable model of the
controller and plant. The development hardware also contains an interface
with which to control the virtual input to the plant. The controller
hardware contains the controller software that is generated from the
controller model. The real-time processor (target hardware) contains
code for the physical system that is generated from the plant model.

Why Perform Hardware-In-The-Loop Simulation?

Use HIL simulation to test the design of your controller when
you are performing Model-Based Design (MBD). The figure shows where
HIL simulation fits into the MBD design-to-realization workflow.

Validation involves using actual plant hardware to test your
controller in real-life situations or in environmental proxies (for
example, a pressure chamber). In HIL simulation, you do not have to
use real hardware for your physical system (plant). You also do not
have to rely on a naturalistic or environmental test setup. By allowing
you to use your model to represent the plant, HIL simulation offers
benefits in cost and practicality.

There are several areas in which HIL simulation offers cost savings over validation testing.
HIL simulation tends to be less expensive for design changes. You can perform HIL
simulation earlier than validation in the MBD workflow so you can identify and
redesign for problems relatively early the project. Finding problems early includes
these benefits:

Your team is more likely to approve changes.

Design changes are less costly to implement.

In terms of scheduling, HIL simulation is less expensive and more
practical than validation because you can set it up to run on its own.

HIL simulation is more practical than validation for testing
your controller’s response to unusual events. For example,
you can model extreme weather conditions like earthquakes or blizzards.
You can also test how your controller responds to stimuli that occur
in inaccessible environments like deep sea or deep space.